THERMAL ANALYSIS OF WASTE HEAT RECOVERY UNIT USING THE EXHAUST GAS EMITTED FROM INTERNAL COMBUSTION ENGINE

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1 THERMAL ANALYSIS OF WASTE HEAT RECOVERY UNIT USING THE EXHAUST GAS EMITTED FROM INTERNAL COMBUSTION ENGINE 1 ROHIT KUMAR DAS, 2 CHINNASAMY SUBRAMANIAN 1 Department of Mechanical Engineering, Velammal Engineering College, Anna University 2 Asst. Professor in Mechanical Engineering, Velammal Engineering College, Anna University,Chennai rohitkumardasoffice@rediffmail.com Abstract- The heat is emitted from diesel engine after every cycle. This heat goes into waste into the atmosphere. Many notable steps have been taken to reduce the wastage of heat. The research paper focuses on the analysis of the amount of heat dissipated from the experimental setup. So therefore analysis software such as ansys fluent software is used to pictographically view the process. An experimental shell and tube heat exchanger setup has been arranged so as to utilize the waste heat. Instead of being wasted by release into the ambient environment sometimes waste heat ( or cold) can be utilized by another process or a portion of heat that would otherwise be wasted can be reused in the same process if the makeup heat is added to the system ( as with heat recovery ventilation in a building ) Index Terms- Heat, Thermal Analysis, Waste Heat Recovery, Exhaust gas emission.) I. INTRODUCTION Waste heat recovery is the collection of heat created as an undesired by-product of the operation of a piece of equipment or machinery to fill a desired purpose elsewhere. Waste heat recouping methods range from the simple to the complex. A common simple example is household water drain heat recovery. In this method, the heat going down a sink or shower drain is recovered by a copper pipe coiling around the drain pipe. The coil is then used to heat water as it passes through pipes on the way to a hot water heater. On the more complex side, heat recovered from liquid cooling systems in data centers can be used for parts of the facilities where warmer temperatures are desired. Other sources of waste heat that can be recovered for practical uses include car exhaust, industrial exhaust, thermoelectric generation and turbines. Depending on the application, the heat itself may be the desired product or may be subjected to another process to provide clean electricity. According to the United States Department of Energy, up to 50 percent of the energy from all fuels burned in the U.S. ends up in the atmosphere as waste heat. Research indicates that recovery of the energy waste from industrial facilities could fulfill up to 20 percent of total domestic electricity demand and simultaneously effect a 20 percent reduction in greenhouse emissions. Waste heat is by necessity produced both by machines that do work and in other processes that use energy, for example in a refrigerator warming the room air or a combustion engine releasing heat into the environment. The need for many systems to reject heat as a by-product of their operation is fundamental to the laws of thermodynamics. Waste heat has lower utility (or in thermodynamics lexicon a lower energy or higher entropy) than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms. Rejection of unneeded cold (as from a heat pump) is also a form of waste heat (i.e. the medium has heat, but at a lower temperature than is considered warm). Instead of being wasted by release into the ambient environment, sometimes waste heat (or cold) can be utilized by another process, or a portion of heat that would otherwise be wasted can be reused in the same process if make-up heat is added to the system (as with heat recovery ventilation in a building). Three essential components to waste heat recovery 1. Accessible source of waste heat; 2. Recovery technology 3. Use for the recovered heat. Obstacles to waste heat recovery high costs, good fit, retrofitting etc. Reasonable payback for the industry & perceived risks are negligible. Implement existing technologies and techniques.carry out further research to enable heat recovery from new sources and increase end use options. The biggest opportunity for efficiency in industry is embedded within the entire industrial process and highlights the huge potential for waste energy recovery systematic energy management approach required. II. PROBLEM DEFINITION In this process we are analyzing waste heat emitting from the diesel engine into useful work. This is achieved by using ansys fluent software. This thesis can reduce the amount of input energy required. The 23

2 thesis charts out the heat dissipated away from the shell and tube heat exchanger as this might help increase the efficiency of the heat exchanger. The charts as streamline, temperature have been displayed in three dimensional views so as to clearly view the amount of heat flowing in and out of the system III. DESIGN AND DEVELOPMENT The specifications required for the apparatus is as follows DIESEL ENGINE SPECIFICATIONS [SINGLE CYLINDER] TECHNICAL SPECIFICATIONS [MULTI CYLINDER APPARATUS] PROPERTIES OF FUEL USED PROPOTIONS OF FUEL AND THEIR ALTERNATIVES: OTHER TECHNICAL SPECIFICATION TEST FUEL SPECIFICATIONS 1.1 COMPONENTS USED: RECUPERATOR: This name is given to different types of heat exchanger that the exhaust gases are passed through, consisting of metal tubes that carry the inlet gas and thus preheating the gas before entering the process. The heat wheel is an example which operates on the same principle as a conditioning unit REGENERATOR: This is an industrial unit that reuses the same stream after processing. In this type of heat recovery, the heat is regenerated and reused in the process HEAT PIPE EXCAHNGER: Heat pipes are one of the best thermal conductors. They have the ability to transfer heat hundred times more than copper. Heat pipes are mainly known in renewable energy technology as being used in evacuated tube collectors. The heat pipe is mainly

3 used in space, process or air heating, in waste heat from a process is being transferred to the surrounding due to its transfer mechanism THERMAL WHEEL: Thermal wheel or rotary heat exchanger: consists of a circular honeycomb matrix of heat absorbing material, which is slowly rotated within the supply and exhaust air streams of an air handling system. processes, and is suited for higher-pressure applications. As its name implies, this type of heat exchanger consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle, and may be composed of several types of tubes: plain, longitudinally finned, etc ECONOMISER: In case of process boilers, waste heat in the exhaust gas is passed along a recuperate that carries the inlet fluid for the boiler and thus decreases thermal energy intake of the inlet fluid HEAT PUMPS: Using an organic fluid that boils at a low temperature means that energy could be regenerated from waste fluids RUN AROUND COIL: It is comprised two or more multi-row finned tube coils connected to each other by a pumped pipework circuit. Particulate Filters (DPF) to capture emission by maintaining higher temperatures adjacent to the converter and tail pipes to reduce the amount of emissions from the exhaust HEAT TO POWER UNIT: the majority of energy production from conventional and renewable resources are lost to the atmosphere due to onsite (equipment inefficiency and losses due to waste heat) and offsite (cable and transformers losses) losses, that sums to be around 66% loss in electricity value. Waste heat of different degrees could be found in final products of a certain process or as a by-product in industry such as the slag in steelmaking plants. Units or devices that could recover the waste heat and transform it into electricity are called WHRUs or heat to power units. For example, an Organic Rankine cycle unit uses an organic fluid as the working fluid. The fluid has a lower boiling point than water to allow it to boil at low temperature, to form a superheated gas that could drive the blade of a turbine and thus a generator. Thermoelectric (See beck, Peltier, Thomson effects) units may also be called WHRU, since they use the heat differential between two plates to produce DC Power A WHRB is different from a Heat Recovery Steam Generator (HRSG) in the sense that the heated medium does not change phase. 1.2 ABOUT SHELL AND TUBE HEAT EXCHANGER A shell and tube heat exchanger is a class of heat exchanger designs. It is the most common type of heat exchanger in oil refineries and other large chemical THEORY AND APPLICATION Two fluids, of different starting temperatures, flow through the heat exchanger. One flows through the tubes (the tube side) and the other flows outside the tubes but inside the shell (the shell side). Heat is transferred from one fluid to the other through the tube walls, either from tube side to shell side or vice versa. The fluids can be either liquids or gases on either the shell or the tube side. In order to transfer heat efficiently, a large heat transfer area should be used, leading to the use of many tubes. In this way, waste heat can be put to use. This is an efficient way to conserve energy. Heat exchangers with only one phase (liquid or gas) on each side can be called one-phase or single-phase heat exchangers. Two-phase heat exchangers can be used to heat a liquid to boil it into a gas (vapor), sometimes called boilers, or cool a vapor to condense it into a liquid (called condensers), with the phase change usually occurring on the shell side. Boilers in steam engine locomotives are typically large, usually cylindrically-shaped shell-and-tube heat exchangers. In large plants with steam-driven turbines, shell-and-tube surface condensers are used to condense the exhaust steam exiting the turbine into condensate water which is recycled back to be turned into steam in the steam generator SHELL AND TUBE HEAT EXCHANGER DESIGN There can be many variations on the shell and tube design. Typically, the ends of each tube are connected to plenums (sometimes called water boxes) through holes in tube sheets. The tubes may be straight or bent in the shape of a U, called U-tubes U TUBE HEAT EXCHANGER In nuclear power plants called pressurized water reactors, large heat exchangers called steam generators are two-phase, shell-and-tube heat exchangers which typically have U-tubes. They are used to boil water recycled from a surface condenser into steam to drive a turbine to produce power. Most shell-and-tube heat exchangers are either 1, 2, or 4 pass designs on the tube side. This refers to the number of times the fluid in the tubes passes through the fluid in the shell. In a single pass heat exchanger, the fluid goes in one end of each tube and out the other. 25

4 FIG.1.1 U TUBE HEAT EXCHANGER STRAIGHT TUBE HEAT EXCHANGER [ ONE PASS TUBE SIDE ] Surface condensers in power plants are often 1-pass straight-tube heat exchangers (see Surface condenser for diagram). Two and four pass designs are common because the fluid can enter and exit onthe same side. This makes construction much simpler. FIG 1.2STRAIGHT TUBE HEAT EXCHANGER ONE PASS TUBE SIDE STRAIGHT TUBE HEAT EXCHANGER [TWO PASS TUBE SIDE] There are often baffles directing flow through the shell side so the fluid does not take a short cut through the shell side leaving ineffective low flow volumes. These are generally attached to the tube bundle rather than the shell in order that the bundle is still removable for maintenance. Counter current heat exchangers are most efficient because they allow the highest log mean temperature difference between the hot and cold streams. Many companies however do not use single pass heat exchangers because they can break easily in addition to being more expensive to build. Often multiple heat exchangers can be used to simulate the counter current flow of a single large exchanger. FIG 1.3STRAIGHT TUBE HEAT EXCHANGER [TWO PASS TUBE SIDE] SELECTION OF TUBE MATERIAL To be able to transfer heat well, the tube material should have good thermal conductivity. Because heat is transferred from a hot to a cold side through the tubes, there is a temperature difference through the width of the tubes. Because of the tendency of the tube material to thermally expand differently at various temperatures, thermal stresses occur during operation. This is in addition to any stress from high pressures from the fluids themselves. The tube material also should be compatible with both the shell and tube side fluids for long periods under the operating conditions (temperatures, pressures, ph, etc.) to minimize deterioration such as corrosion. All of these requirements call for careful selection of strong, thermally-conductive, corrosion-resistant, high quality tube materials, typically metals, including copper alloy, stainless steel,, nonferrous copperalloy, Incon el, nickel, Hastelloy and titanium. [ Fluoropolymers s uch as Perfluoroalkoxy alkane (PFA) and Fluorinated ethylene propylene (FEP) are also used to produce the tubing material due to their high resistance to extreme temperatures. Poor choice of tube material could result in a leak through a tube between the shell and tube sides causing fluid cross-contamination and possibly loss of pressure APPLICATION AND USES The simple design of a shell and tube heat exchanger makes it an ideal cooling solution for a wide variety of applications. One of the most common applications is the cooling of hydraulic fluid and oil in engines, transmissions and hydraulic power packs. With the right choice of materials they can also be used to cool or heat other mediums, such as swimming pool water or charge air. One of the big advantages of using a shell and tube heat exchanger is that they are often easy to service, particularly with models where a floating tube bundle (where the tube plates are not welded to the outer shell) is available. 26

5 1.3 DIESEL ENGINE The diesel engine (also known as a compression-ignition or 'CI' engine) is an internal combustion engine in which ignition of the fuel that has been injected into the combustion chamber is initiated by the high temperature which a gas achieves when greatly compressed (adiabatic compression). This contrasts with spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to petrol), which use a spark plug to ignite an air-fuel mixture. The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high compression ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared to two-stroke non-direct-injection gasoline engines since un burnt fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can have a thermal efficiency that exceeds 50% Diesel engines are manufactured in two-stroke and four-stroke versions. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road vehicles in the USA increased. According to the British Society of Motor Manufacturing and Traders, the EU average for diesel cars accounts for 50% of the total sold, including 70% in France and 38% in the UK The world's largest diesel engine is currently a Wärtsilä-Sulzer RTA96-C Common Rail marine diesel, which produces a peak power output of MW (113,210 hp) at 102 rpm RESULT AND DISCUSSION ADVANTAGES: These systems have many benefits which could be direct or indirect DIRECT BENEFITS: The recovery process will add to the efficiency of the process and thus decrease the costs of fuel and energy consumption needed for that process INDIRECT BENEFITS: Reduction in Pollution: Thermal and air pollution will dramatically decrease since less flue gases of high temperature are emitted from the plant since most of the energy is recycled Reduction in the equipment sizes: As Fuel consumption reduces so the control and security equipment for handling the fuel decreases. Also, filtering equipment for the gas is no longer needed in large sizes. Reduction in auxiliary energy consumption: Reduction in equipment sizes means another reduction in the energy fed to those systems like pumps, filters, fans etc. OTHER BENEFITS: o Waste of the byproduct heat is reduced o Co-generation system is introduced i.e. Combined heat and power system is invoked o Effective utilization of small temperature difference to generate other forms of energy o Pre heating of incoming fluid and objects so as to economize the input source o Electrification of waste heat is enabled o Lower temperature is used to produce electricity CONCULSION Thus this research shows how thermal energy can be utilized for recycling. Although based on second law of thermodynamics that the efficiency cannot be one hundred percent but the efficiency can be increased using different material. The virtual visualization has been achieved using fluent software. REFERENCES [1]. Heat Recovery Systems, D.A.Reay, E & F.N.Span, 1979 [2]. Energetic Incorporated (November 2004), Technology Roadmap Energy Loss Reduction and Recovery (pdf), U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, retrieved May 2012 [3]. [4]. R. Andrews and J.M. Pearce, Environmental and Economic Assessment of a Greenhouse Waste Heat Exchange, Journal of Cleaner Production 19, pp (2011). open access. [5]. [6]. htmtapping [7]. Industrial Waste Heat Could Reduce Fossil Fuel Demands [8]. [9]. Cyclone Power Technologies Website [10]. "Waste Wattage: Cities Aim to Flush Heat Energy Out of Sewers"news.nationalgeographic.com. Retrieved [11]. [12]. Sadik Kakaç and Hongtan Liu (2002). Heat Exchangers: Selection, Rating and Thermal Design (2nd ed.). CRC Press. ISBN [13]. Perry, Robert H. and Green, Don W. (1984). Perry's Chemical Engineers' Handbook (6th ed.). McGraw-Hill. ISBN [14]. "Shell and Tube Exchangers". Retrieved [15]. "PFA Properties" (PDF). Fluorotherm Polymers, Inc. Retrieved 4 November [16]. Heat Exchanger Shell Bellows Piping Technology and Products, (retrieved March 2012) 27